phy: dt bindings: add NXP LPC18xx/43xx USB OTG PHY bindings

NXP LPC18xx/43xx internal USB OTG PHY binding

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This file contains documentation for the internal USB OTG PHY found

in NXP LPC18xx and LPC43xx SoCs.

Required properties:

- compatible	: must be "nxp,lpc1850-usb-otg-phy"

- clocks	: must be exactly one entry

See: Documentation/devicetree/bindings/clock/clock-bindings.txt

- #phy-cells	: must be 0 for this phy

See: Documentation/devicetree/bindings/phy/phy-bindings.txt

The phy node must be a child of the creg syscon node.

Example:

creg: syscon@40043000 {

	compatible = "nxp,lpc1850-creg", "syscon", "simple-mfd";

	reg = <0x40043000 0x1000>;

	usb0_otg_phy: phy@004 {

		compatible = "nxp,lpc1850-usb-otg-phy";

		clocks = <&ccu1 CLK_USB0>;

		#phy-cells = <0>;

	};

};